Exposure apparatus, exposure method, and method of manufacturing device

ABSTRACT

A scanning exposure apparatus measures levels of a substrate at a predetermined position on the substrate at a first measurement point during the acceleration period and a second measurement point during the constant velocity period, obtains a correction value for a measurement error due to factors associated with acceleration based on the measurement results, corrects the measured level using the obtained correction value and exposes the substrate so that the level at a given position on the substrate becomes equal to the corrected level, when the substrate is exposed at the given position after the level is measured while the stage accelerates, and exposes the substrate so that the level at a given position on the substrate becomes equal to the measured level measured, when the substrate is exposed after the level of the substrate at the given position is measured while the stage moves at a constant velocity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus, an exposuremethod, and a method of manufacturing a device.

2. Description of the Related Art

To improve productivity, a conventional exposure apparatus measures thesurface position of a wafer, mounted on a stage, while the stage moves.When the surface position of the wafer is measured while the stage movesand especially while the stage accelerates or decelerates, deformationof the main structure of the apparatus occurs, thus generating ameasurement error in the measurement result of the surface position. Anexposure apparatus disclosed in Japanese Patent Laid-Open No. 11-191522obtains a correction value to correct for errors in measurement, priorto exposure. This correction value is calculated based on a pitchingcomponent of the stage orientation. The exposure apparatus corrects themeasurement result of the surface position, measured while the stagemoves, using the correction value, and exposes the wafer in accordancewith the corrected surface position.

However, Japanese Patent Laid-Open No. 11-191522 discloses no techniquefor measuring the level of a substrate while the stage accelerates,positioning the stage which is moving at a constant velocity, based onthe measured level, and exposing the substrate. To meet the recentdemand for a further improvement in productivity, the acceleration valueor the deceleration value of the stage is likely to increase so as toquickly position the stage. As a result, not only deformation of themain structure of the apparatus but also that of the stage itself andeven that of a measurement device mounted on the stage, such as areference mirror for a laser interferometer, occur, so the measurementresult obtained by the measurement device includes a measurement errordue to factors associated with acceleration of the stage.

SUMMARY OF THE INVENTION

The present invention provides an exposure apparatus which measures thelevel of a substrate while a stage accelerates, but nonetheless canprecisely measure the level of the substrate held on the stage which ismoving at a constant velocity, based on the measured level.

According to one aspect of the present invention, there is provided anexposure apparatus which projects a pattern of a reticle onto asubstrate via a projection optical system using slit-shaped light whilescanning the reticle and the substrate, thereby exposing the substrate,the apparatus comprising: a stage which holds the substrate; apositioning mechanism which positions the stage in a first direction toscan the substrate and a second direction parallel to an optical axis ofthe projection optical system; a measurement device which measures alevel of the substrate that is a position of the substrate in the seconddirection at a plurality of measurement points located with spacingstherebetween in the first direction; and a controller, wherein theplurality of measurement points include a first measurement point atwhich the level of the substrate can be measured earliest, and a secondmeasurement point within a region in which the slit-shaped light isincident on the substrate, the exposure apparatus is configured tomeasure the level of the substrate at the first measurement point usingthe measurement device, and expose the substrate while positioning thestage in the second direction using the positioning mechanism based onthe level measured at the first measurement point, and the controllercauses, before the substrate is exposed, the measurement device tomeasure the level of the substrate at a predetermined position on thesubstrate at the first measurement point while the stage accelerates,and measure the level of the substrate at the predetermined position atthe second measurement point while the stage moves at a constantvelocity, calculates a difference between the measurement results of thelevel of the substrate at the predetermined position, which are obtainedat the first measurement point and the second measurement point,respectively, to obtain the calculated difference as a correction valuefor a measurement error due to factors associated with acceleration ofthe stage, and corrects the level of the substrate measured at the firstmeasurement point using the obtained correction value and exposes thesubstrate while controlling the positioning mechanism so that the levelof the substrate at a given position on the substrate becomes equal tothe level corrected using the correction value, when the substrate isexposed at the given position after the level of the substrate at thegiven position is measured at the first measurement point while thestage accelerates, and exposes the substrate while controlling thepositioning mechanism so that the level of the substrate at a givenposition on the substrate becomes equal to the level measured at thefirst measurement point, when the substrate is exposed after the levelof the substrate at the given position is measured at the firstmeasurement point while the stage moves at a constant velocity.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an exposure apparatus according to the firstembodiment;

FIG. 2 is a view showing the positional relationship between a wafer andmeasurement points;

FIG. 3 is a view showing the positional relationship between measurementpoints and an exposure slit;

FIGS. 4A and 4B are views showing a measurement method in scanningexposure;

FIG. 5 is a view showing the measurement method in scanning exposure;

FIGS. 6A, 6B, and 6C are views showing a method of obtaining ameasurement error while a stage accelerates;

FIG. 7 is a flowchart of an exposure method;

FIG. 8 is a view showing a wafer and shot regions on the wafer; and

FIG. 9 is a block diagram showing an exposure apparatus according to thethird embodiment.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 shows an exposure apparatus according to the first embodiment.The exposure apparatus is a scanning projection exposure apparatus whichprojects the pattern of a reticle (original) 2 onto a wafer (substrate)4 via a projection optical system 1 using slit-shaped light whilerelatively scanning the reticle 2 and the wafer 4 in the X direction(first direction), thereby exposing the wafer 4. The slit shape whichdetermines an exposure region exposed to the slit-shaped light is arectangular or arcuated shape. An optical axis AX of the reductionprojection optical system 1 runs in the Z direction (second direction),and its image plane is perpendicular to the Z direction parallel to theoptical axis AX. The reticle 2 is held on a stage (reticle stage) 3. Thepattern of the reticle 2 is reduced to ¼, ½, or ⅕ as the magnificationof the reduction projection optical system 1, and projected onto theimage plane of the reduction projection optical system 1, therebyforming an image on this image plane. A large number of shot regionswith the same pattern structure formed in the preceding exposure processare arrayed on the wafer (substrate) 4 having its surface coated with aresist. A stage (wafer stage) 5 which holds the wafer 4 includes a chuckwhich chucks and fixes the wafer 4 to the wafer stage 5. That is, thewafer stage 5 serves as a stage which can move while mounting asubstrate. The wafer stage 5 also includes X and Y stages which can movehorizontally in the X and Y directions, respectively, and can move inthe Z direction as well. Moreover, the wafer stage 5 includes a levelingstage which can rotate about the X- and Y-axes, and a rotating stagewhich can rotate about the Z-axis. In this manner, the wafer stage 5serves as a six-axis correction system for matching a reticle patternimage with each shot region on the wafer. The positional information ofthe wafer stage 5 in the X and Y directions is always measured by a barmirror 23 and interferometer 24 which are fixed on the wafer stage 5.

A measurement device 16 provided to measure the surface position andtilt of the wafer 4 includes a light source 10 such as a lamp or alight-emitting diode. A collimator lens 11 receives a light beam fromthe light source 10, converts it into a collimated light beam with anearly uniform cross-sectional intensity distribution, and outputs it. Aprism-shaped slit member 12 is formed by bonding a pair of prismstogether so that their inclined surfaces face each other. A plurality ofopenings (for example, nine pinholes) are provided in the bondingsurface using a light-shielding film made of, for example, chromium. Abilateral telecentric lens 13 guides nine independent light beams havingpassed through the plurality of pinholes, respectively, in the slitmember 12 to nine measurement points, respectively, on the wafer 4 via amirror 14. At this time, a plane in which the pinholes are formed andthat which includes the surface of the wafer 4 are set to satisfy theScheimpflug condition for the lens 13. In the first embodiment, eachlight beam emitted by the light source 10 has an incident angle Φ (anangle that this light beam makes with the optical axis) on the wafer 4is 70° or more. As shown in FIG. 2, the nine light beams having passedthrough the lens 13 are incident on independent measurement points inthe pattern region to form images in it. Also, the nine light beams areincident on the nine measurement points from a direction obtained byrotating the X direction through θ° (for example,) 22.5° within the X-Yplane so that these measurement points are independently observed withinthe plane of the wafer 4. The light source 10, collimator lens 11, slitmember 12, lens 13, and mirror 14 serve as a light projecting opticalsystem which obliquely projects a light beam to a measurement point onthe wafer 4.

Each configuration of a bilateral telecentric light receiving opticalsystem which receives the light beams reflected by the wafer 4 will bedescribed next. The light receiving optical system receives, via amirror 15, the nine light beams reflected by the wafer 4. An aperturestop 17 is provided in the light receiving optical system commonly tothe nine measurement points. The aperture stop 17 cuts high-orderdiffracted light (noise light) generated by the circuit pattern presenton the wafer 4. The light beams having passed through the bilateraltelecentric light receiving optical system have parallel optical axes.Nine individual correction lenses in correction optical systems 18 formimages of the nine light beams again on the measurement surface ofphotoelectric conversion elements 19 so that they become spotlight beamswith the same size. Also, the light receiving optical system performsangle error correction so that each measurement point on the wafer 4becomes conjugate to the measurement surface of the photoelectricconversion elements 19. Therefore, the position of a pinhole image doesnot change on the measurement surface due to a local tilt of eachmeasurement point, but changes on the measurement surface in response toa change in level of each measurement point in the direction of theoptical axis AX. Although the photoelectric conversion elements 19include, for example, nine one-dimensional CCD line sensors, the sameeffect can also be attained when a plurality of two-dimensional positionmeasurement elements are arranged. The light projecting optical systemincluding the members 10 to 14 and the light receiving optical systemincluding the members 15 to 19 serve as the measurement device 16 whichmeasures the level of the wafer 4 at a plurality of measurement pointswhich are aligned with spacings between them in the X direction (firstdirection). A measurement device controller 26 controls the measurementdevice 16.

As shown in FIG. 1, the reticle 2 is chucked and fixed to the reticlestage 3. The reticle stage 3 scans at a constant velocity in the Xdirection (an arrow 3 a) within a plane perpendicular to the opticalaxis AX of the projection optical system 1. At this time, the reticlestage 3 undergoes correction driving in the Y direction so as to scanwhile always maintaining a target position. The positional informationof the reticle stage 3 in the X and Y directions is always measured by abar mirror 20 and interferometer 21 which are fixed on the reticle stage3 shown in FIG. 1. An illumination optical system 6 includes a lightsource which generates pulsed light, such as an excimer laser. Theillumination optical system 6 also includes members (not shown) such asa beam shaping optical system, optical integrator, collimator, andmirror, and is formed from a material which efficiently transmits orreflects pulsed light in the far-ultraviolet range. The beam shapingoptical system shapes the cross-sectional shape (including the size) ofthe incident beam into a desired shape. The optical integrator uniformsthe distribution characteristics of a light beam to illuminate thereticle 2 with a uniform illuminance. A masking blade (not shown) withinthe illumination optical system 6 sets a rectangular illumination regionin correspondence with the chip size. The pattern on the reticle 2partially illuminated in the illumination region is projected onto thewafer 4 via the projection optical system 1.

To form a slit image of the reticle 2 in a predetermined region on thewafer 4, a main controller 27 controls the following operation. That is,the main controller 27 adjusts the position within the X-Y plane (the Xand Y positions and the rotation e about the Z-axis) and that in the Zdirection (the rotations θ and β about the X- and Y-axes, respectively,and the level Z on the Z-axis). Also, the main controller 27 scans thereticle stage 3 and the wafer stage 5 in synchronism with the projectionoptical system 1. Moreover, the main controller 27 performs scanningexposure, in which the pattern on the reticle 2 is projected andtransferred by exposure onto the wafer 4 via the projection opticalsystem 1. In scanning the reticle stage 3 in the direction indicated bythe arrow 3 a shown in FIG. 1, the main controller 27 scans the waferstage 5 at a velocity corrected by an amount equal to the reductionmagnification of the projection optical system 1 in the directionindicated by an arrow 5 a shown in FIG. 1. The scanning velocity of thereticle stage 3 is determined so as to achieve a high productivity,based on the width of the masking blade in the scanning direction withinthe illumination optical system 6, and the sensitivity of a resistapplied on the surface of the wafer 4. The main controller 27 calculatescontrol data based on the position data obtained by the interferometer21 for the reticle stage 3 and the interferometer 24 for the wafer stage5, and that of the wafer 4 obtained by an alignment microscope (notshown). Based on the control data, the main controller 27 controls areticle stage controller 22 and a wafer stage controller 25 to align thepattern on the reticle 2 within the X-Y plane. The wafer stagecontroller 25 serves as a positioning mechanism which positions thewafer stage 5 in the X direction (first direction) and the Z direction(second direction). The main controller 27, reticle stage controller 22,wafer stage controller 25, and measurement device controller 26 serve asa controller.

FIG. 3 shows the relationship between nine surface position measurementpoints formed in a shot region 301 on the wafer 4 by the photoelectricconversion elements 19, and an exposure slit 302. The exposure slit 302is a rectangular exposure region surrounded by a broken line in FIG. 3.Measurement points 303 to 305 are surface position measurement points(second measurement points) within a region which is formed within theexposure slit 302 and in which slit-shaped light is incident on thewafer 4. Measurement points 306 to 311 are measurement points (firstmeasurement points) which are spaced apart from the exposure slit 302 ata distance Lp and at which the level of the wafer 4 can be measuredearliest. Of the measurement points 306 to 311, the measurement pointsused are switched in accordance with the moving direction of the waferstage 5. For example, in scanning exposure in a direction F, the surfaceposition of the shot region 301 is measured at the measurement points306 to 308 prior to measurement at the measurement points 303 to 305,respectively, within the exposure slit 302. Before the region to beexposed reaches inside the exposure slit 302, the main controller 27drives the wafer stage 5 to an optimum exposure image plane positionbased on the measurement results obtained at the measurement points 306to 308. On the other hand, in scanning exposure in a direction R, thesurface position of the shot region 301 is measured at the measurementpoints 309 to 311 prior to measurement at the measurement points 303 to305, respectively, within the exposure slit 302. Before the region to beexposed reaches inside the exposure slit 302, the main controller 27drives the wafer stage 5 to an optimum exposure image plane positionbased on the measurement results obtained at the measurement points 309to 311. The exposure apparatus is configured to perform exposureprocessing while positioning the position of the wafer 4 in the Zdirection at the exposure position based on the level of the wafer 4measured at the measurement points 306 to 308 or 309 to 311 at which thelevel of the wafer 4 can be measured earliest.

A method of measuring the surface position in scanning exposure will bedescribed with reference to FIGS. 4A and 4B. FIG. 4A is a view showingshot regions, surface position measurement points, and a driving trackof the wafer stage 5. A shot region 401 is an already exposed shotregion, a shot region 402 is a currently exposed shot region, and a shotregion 403 is a shot region to be exposed next to the shot region 402.An arrowed broken line in FIG. 4A indicates a driving track of the waferstage 5. FIG. 4B is a graph showing the relationship between time andthe velocity of the wafer stage 5 upon driving it along the track shownin FIG. 4A. After exposure of the shot region 401 is completed, thewafer stage 5 is driven in the X direction with deceleration, therebymoving to the shot region 402 to be exposed next. The decelerationperiod corresponds to the interval from time t1 to time t2 in FIG. 4B.Subsequently, when an acceleration start point (not shown) is reached,the main controller 27 accelerates the wafer stage 5 in the direction R.The acceleration period corresponds to the interval from time t2 to timet3 in FIG. 4B. The velocity of the wafer stage 5 desirably reaches atarget velocity at least until the exposure slit 302 arrives at the shotregion 402. After the velocity of the wafer stage 5 reaches the targetvelocity, the wafer stage 5 continues scanning at a constant velocityuntil it leaves the shot region 402. The constant velocity periodcorresponds to the interval from time t3 to time t4 in FIG. 4B. At thistime, the main controller 27 performs exposure processing whilesequentially performing surface position measurement of the shot region402 and driving to an optimum exposure image plane position. After theexposure slit 302 leaves the shot region 402, the main controller 27decelerates the wafer stage 5 in preparation for exposure of the shotregion 403, drives it in the X direction, and accelerates it. Thedeceleration period corresponds to the interval after time t4.

Surface positions 404 to 409 shown in FIG. 4A exemplify measurementpositions in the shot region 402. Although a plurality of measurementpositions are present in the Y direction in the shot region 402 tomeasure the surface position of the entire shot region 402, FIG. 4Ashows only the surface positions 404 to 409 for the sake of simplicity.A case in which the measurement device 16 measures the surface positions404 to 406 at the surface position measurement points 306 to 308,respectively, will be considered first. This measurement will beexplained in detail with reference to FIG. 5. As described earlier,after exposure of the shot region 401 is completed, the main controller27 decelerates the wafer stage 5 in preparation for exposure of the shotregion 402, drives it in the X direction, and accelerates it. When thesurface position measurement points 306 to 308 reach the surfacepositions 404 to 406, respectively, the wafer stage 5 has a velocitydefined in the interval between times t2 and t3 in FIG. 4B, and istherefore accelerating at this time. Upon acceleration of the waferstage 5, deformations of the main structure of the exposure apparatusand the wafer stage 5 itself occur. The surface positions 404 to 406which are measured at the surface position measurement points 306 to308, respectively, by the measurement device 16 include measurementerrors due to these deformations. If the main controller 27 generates adriving target value for the exposure image plane position based on thesurface position measurement results including the measurement errors,defocus occurs, thus leading to resolution insufficiency. Themeasurement positions 404 to 406 are predetermined positions on thesubstrate, at which the level of the wafer 4 is measured at firstmeasurement points by the measurement device 16 while the wafer stage 5accelerates.

A case in which the measurement device 16 measures the surface positionscorresponding to the measurement positions 407 to 409 at the surfaceposition measurement points 306 to 308, respectively, will be considerednext. When the surface position measurement points 306 to 308 reach themeasurement positions 407 to 409, respectively, the wafer stage 5 has avelocity defined in the interval between times t3 and t4 in FIG. 4B, andis therefore moving at a constant velocity at this time. During movementof the wafer stage 5 at a constant velocity, the above-mentioneddeformations of the main structure and the wafer stage 5 itself do notoccur to the degree that they adversely affect the surface positionmeasurement results. Note that to allow the wafer stage 5 to be movingat a constant velocity when the measurement device 16 measures thesurface positions corresponding to the measurement positions 404 to 406at the surface position measurement points 306 to 308, respectively, itis necessary to adopt one of measures of:

a) keeping the acceleration start point farther away from the shotregion,

b) shortening the distance Lp between the surface position measurementpoints 303 to 305 and 306 to 308, respectively, and

c) raising the acceleration of the wafer stage 5.

If measure a is chosen, the distance by which the wafer stage 5 moves inthe Y direction increases, so the productivity lowers. If measure b ischosen, the time until the region to be exposed reaches inside theexposure slit 302 shortens. Hence, if the wafer 4 has poor evenness,driving to an optimum exposure image plane position cannot besatisfactorily performed, thus leading to defocus. If measure c ischosen, both the size and cost of the exposure apparatus increase. Inthe above-mentioned manner, to reconcile the productivity and accuracyof the exposure apparatus without driving the cost up, the wafer stage 5must measure the surface position during acceleration.

A method of obtaining a measurement error, which is generated uponmeasuring the surface position while the wafer stage 5 accelerates,prior to exposure will be described next. FIGS. 6A to 6C show therelationships between measurement positions 602 to 604 in a shot region601, and surface position measurement points. The surface positionmeasurement points 303, 306, and 309 are located at the sameX-coordinate position. Also, the measurement points 304, 307, and 310are located at the same X-coordinate position. Moreover, the measurementpoints 305, 308, and 311 are located at the same X-coordinate position.Therefore, when each photoelectric conversion element 19 adjusts themeasurement timing of the surface position to be measured for scanningin the Y direction, different photoelectric conversion elements 19 candoubly measure the same coordinate position in the shot region. Thismeasurement will be explained in detail with reference to FIGS. 6B and6C. A case in which the measurement position 602 within the shot region601 is measured by scanning in a direction R shown in FIG. 6A will beconsidered. The measurement device 16 measures the measurement position602 at the surface position measurement point 306 at a timing shown inFIG. 6B. After scanning for a predetermined time, the measurement device16 measures the measurement position 602 at the surface positionmeasurement point 303 at a timing shown in FIG. 6C. Similarly, themeasurement position 603 shown in FIG. 6A is measured at the surfaceposition measurement point 307, and is thereupon measured at the surfaceposition measurement point 304. The measurement position 604 shown inFIG. 6A is measured at the surface position measurement point 308, andis thereupon measured at the surface position measurement point 305. Atthe moment shown in FIG. 6B, the measurement device 16 measures themeasurement positions 602 to 604 at the surface position measurementpoints 306 to 308, respectively. At this timing, measurement isperformed in the interval between times t2 and t3 shown in FIG. 4B, thatis, while the wafer stage 5 accelerates. Therefore, the sums of thevalues of the surface positions corresponding to the measurementpositions 602 to 604 and measurement errors due to the above-mentioneddeformations are obtained as the measurement results obtained at thesurface position measurement points 306 to 308, respectively. At themoment shown in FIG. 6C, the measurement device 16 measures themeasurement positions 602 to 604 at the surface position measurementpoints 303 to 305, respectively. At this timing, measurement isperformed in the interval between times t3 and t4 shown in FIG. 4B, thatis, while the wafer stage 5 moves at a constant velocity. Duringmovement of the wafer stage 5 at a constant velocity, theabove-mentioned deformations do not occur. Thus, the surface positionsmeasured at the surface position measurement points 303 to 305 includeno measurement errors, so the surface positions corresponding to themeasurement positions 602 to 604, respectively, alone are obtained.

As described earlier, a measurement result a obtained at each of themeasurement points 306 to 308 while the wafer stage 5 accelerates, and ameasurement result β obtained at each of the measurement points 303 to305 while it moves at a constant velocity are obtained by measuring thesame coordinate position on the wafer 4. Therefore, by calculating thedifference between α and β, surface position components of themeasurement positions 602 to 604 can be eliminated from the measurementresults, thereby extracting only components of the measurement errors.That is, a correction value Comp for a surface position measurementerror due to factors associated with acceleration of the wafer stage 5can be obtained by:

Comp=α−β  (1)

The amount of deformation of, for example, the main structure due tofactors associated with acceleration of the wafer stage 5 differsdepending on the acceleration of the wafer stage 5. Hence, thecorrection value Comp may be obtained and held for each acceleration ofthe wafer stage 5. When the scanning direction in exposure differs,deformations occur in different portions, so the measurement errorgenerated upon surface position measurement changes. Hence, thecorrection value Comp may be obtained and held for each scanningdirection in exposure. The driving track of the wafer stage 5 before andafter exposure differs depending on the sizes, positions, and exposureorder of shot regions on the wafer 4. The amount of deformation differsdepending not only on factors associated with acceleration in the Ydirection but also on those associated with driving in the X directionbefore and after exposure. Hence, the correction value Comp may beobtained and held for each driving track of the wafer stage 5 before andafter exposure.

Using the thus obtained correction value Comp, the surface positionmeasured while the wafer stage 5 accelerates is corrected as:

Fcomp=Forg−Comp  (2)

where Fcomp is the surface position measurement value corrected usingthe correction value Comp, and Forg is the surface position measurementvalue before correction.

Based on the corrected surface position measurement result Fcomp, themain controller 27 performs exposure processing while performingcorrection driving of the wafer stage 5 to an optimum exposure imageplane position. The surface position measurement result may be correctedusing the correction value Comp only for a surface position measurementpoint measured while the wafer stage 5 accelerates.

Second Embodiment

An example of an exposure method will be described next with referenceto FIG. 7. In step 1, a main controller 27 starts control of exposureprocessing. In step 2, a conveyance hand (not shown) loads a wafer 4onto a wafer stage 5 to chuck and fix it to a chuck (not shown). In step3, the main controller 27 performs preliminary measurement andcorrection for global alignment to be done in step 7. The amount ofshift such as a rotation error of the wafer 4 is measured and correctedby a low-powered field alignment microscope (not shown) to fall withinthe measurement range of a high-powered field alignment microscope (notshown) for use in global alignment. In step 4, the surface positions ofa plurality of shot regions (for example, shot regions 801 shown in FIG.8) on the wafer 4 are measured using a measurement device 16. Based onthe measurement results, the main controller 27 calculates and correctsthe overall tilt of the wafer 4.

In step 5, the main controller 27 performs preliminary adjustment formeasuring the surface position in real time in scanning exposure of step8. The preliminary adjustment includes, for example, light amountadjustment of a light source 10 in the measurement device 16, asdescribed in Japanese Patent Laid-Open No. 10-64980, and storage of apattern step on the surface of a shot region on the wafer 4, asdescribed in Japanese Patent Laid-Open No. 9-45608. In step 5 as well, acorrection value is obtained for a measurement error generated uponmeasuring the surface position while the wafer stage 5 accelerates.Surface position measurement for obtaining the correction value isperformed while the wafer stage 5 is driven to have the same velocity,acceleration, and track as those set in exposure. After the measurement,a correction value Comp is obtained by equation (1) using a measurementresult a of the surface position measured during acceleration and ameasurement result β of the surface position measured during movement ata constant velocity, both for the same coordinate position. Correctionvalues Comp may be obtained for all points corresponding to measurementpositions in the Y direction within a shot region. Alternatively, only ameasurement position while the wafer stage 5 accelerates may beobtained. The correction value Comp may have a value unique to each shotregion. Alternatively, the correction value Comp may have a value whichdepends on the X- and Y-coordinates. Or again, the correction value Compmay hold a value corresponding to a single shot region as a value commonto each shot region. Surface position measurement for obtaining thecorrection value Comp may be performed by measuring all shot regions inthe same order as in exposure. Alternatively, a single shot region maybe used, as exemplified by a shot region 802 shown in FIG. 8. Or again,a plurality of shot regions may be used and the results may be averaged,as exemplified by the shot regions 801 shown in FIG. 8.

In step 6, correction values for, for example, the tilt and curvature offield of a projection optical system 1 are obtained using a light amountsensor and reference mark (neither is shown) on the wafer stage 5 and areference plate (not shown) on a reticle stage 3. More specifically, thelight amount sensor measures a change in amount of exposure light uponscanning the wafer stage 5 in the X, Y, and Z directions. Based on thechange in amount of light obtained by the light amount sensor, theamount of shift of the reference mark with respect to the referenceplate is measured, and a correction value is calculated and corrected.In step 7, an alignment mark on the wafer 4 is measured using ahigh-powered field alignment microscope (not shown) to calculate theamount of shift of the entire wafer and that common to each shot region.To precisely measure the alignment mark, the contrast of the alignmentmark must be at a best contrast position. A best contrast position ismeasured using the measurement device 16 and the alignment microscope.More specifically, while the wafer stage 5 is driven to a predeterminedlevel, and the contrast is measured by the alignment microscope, aprocess of measuring the surface position by the measurement device 16is repeated several times. At this time, the contrast measurement resultand surface position measurement result corresponding to each level areassociated with each other, and stored in the main controller 27. Aposition at which the contrast is highest is calculated from theplurality of obtained contrast measurement results, and determined as abest contrast position.

In step 8, the measurement device 16 measures, in real time, the surfaceposition in the shot region to be exposed. The surface positionmeasurement result is corrected by the correction value Comp usingequation (2). Based on a corrected surface position measurement resultFcomp, the main controller 27 performs exposure processing whileperforming correction driving of the wafer stage 5 to an optimumexposure image plane position. After exposure processing of all shotregions is completed, the substrate is unloaded from the wafer stage 5in step 9, and a series of exposure processing ends in step 10.

In the flowchart shown in FIG. 7, the sequence of obtaining thecorrection value Comp in step 5 is executed for each wafer. To improvethe productivity, the sequence of obtaining the correction value Compmay be executed for each set of a plurality of wafers. For example,before exposure processing of a lot, the sequence of obtaining thecorrection value Comp is executed using at least one wafer belonging tothe lot, for example, the first wafer in the lot. Then, for the secondand subsequent wafers in the lot, the sequence may be skipped and thecorrection value Comp obtained for the first wafer in the lot may beused in exposure. Alternatively, a method of executing the sequence onlyat a specific timing such as assembly, adjustment, or maintenance of theexposure apparatus may be adopted. When the layout conditions such asthe sizes, positions, and exposure order of shot regions on the wafer,and the driving conditions such as the velocity and acceleration of thewafer stage are the same, the above-mentioned measurement error isnearly the same. Hence, the correction value Comp obtained in step 5 isheld in association with the above-mentioned layout conditions and waferstage driving conditions. In exposing wafers which are subject to thesame conditions, exposure which uses the held correction value Comp maybe performed, and the sequence of obtaining the correction value Compmay be skipped.

Third Embodiment

An exposure apparatus according to the third embodiment will bedescribed next with reference to FIG. 9. The exposure apparatusaccording to the third embodiment is connected to a host computer, asshown in FIG. 9. The host computer is connected to a plurality of (forexample, four in FIG. 9) exposure apparatuses 1 to 4. The host computermanages parameters such as the operating condition and offset of theexposure apparatus. The host computer also manages a correction valuefor a measurement error generated upon measuring the surface positionwhile a wafer stage 5 accelerates, as mentioned earlier. In exposingwafers which are subject to the same conditions as those for anotherexposure apparatus, the correction value obtained by this exposureapparatus may be used, and the sequence of obtaining the correctionvalue, shown in step 5 of FIG. 7, may be skipped.

Fourth Embodiment

A method of manufacturing a device (for example, a semiconductor deviceor a liquid crystal display device) will be described next. Asemiconductor device is manufactured by a preprocess of forming anintegrated circuit on a wafer, and a post-process of completing, as aproduct, a chip of the integrated circuit formed on the wafer by thepreprocess. The preprocess includes a step of exposing a wafer, coatedwith a photosensitive agent, using the above-mentioned exposureapparatus, and a step of developing the wafer. The post-process includesan assembly step (dicing and bonding) and packaging step(encapsulation). A liquid crystal display device is manufactured by astep of forming a transparent electrode. The step of forming atransparent electrode includes a step of applying a photosensitive agentonto a glass substrate on which a transparent conductive film isdeposited, a step of exposing the glass substrate, coated with thephotosensitive agent, using the above-mentioned exposure apparatus, anda step of developing the glass substrate. The method of manufacturing adevice according to this embodiment can manufacture a device with aquality higher than those of devices manufactured by the prior arts.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-107716, filed May 7, 2010, which is hereby incorporated byreference herein in its entirety.

1. An exposure apparatus which projects a pattern of a reticle onto asubstrate via a projection optical system using slit-shaped light whilescanning the reticle and the substrate, thereby exposing the substrate,the apparatus comprising: a stage which holds the substrate; apositioning mechanism which positions said stage in a first direction toscan the substrate and a second direction parallel to an optical axis ofthe projection optical system; a measurement device which measures alevel of the substrate that is a position of the substrate in the seconddirection at a plurality of measurement points located with spacingstherebetween in the first direction; and a controller, wherein theplurality of measurement points include a first measurement point atwhich the level of the substrate can be measured earliest, and a secondmeasurement point within a region in which the slit-shaped light isincident on the substrate, the exposure apparatus is configured tomeasure the level of the substrate at the first measurement point usingsaid measurement device, and expose the substrate while positioning saidstage in the second direction using said positioning mechanism based onthe level measured at the first measurement point, and said controllercauses, before the substrate is exposed, said measurement device tomeasure the level of the substrate at a predetermined position on thesubstrate at the first measurement point while said stage accelerates,and measure the level of the substrate at the predetermined position atthe second measurement point while said stage moves at a constantvelocity, calculates a difference between the measurement results of thelevel of the substrate at the predetermined position, which are obtainedat the first measurement point and the second measurement point,respectively, to obtain the calculated difference as a correction valuefor a measurement error due to factors associated with acceleration ofsaid stage, and corrects the level of the substrate measured at thefirst measurement point using the obtained correction value and exposesthe substrate while controlling said positioning mechanism so that thelevel of the substrate at a given position on the substrate becomesequal to the level corrected using the correction value, when thesubstrate is exposed at the given position after the level of thesubstrate at the given position is measured at the first measurementpoint while said stage accelerates, and exposes the substrate whilecontrolling said positioning mechanism so that the level of thesubstrate at a given position on the substrate becomes equal to thelevel measured at the first measurement point, when the substrate isexposed after the level of the substrate at the given position ismeasured at the first measurement point while said stage moves at aconstant velocity.
 2. The apparatus according to claim 1, wherein beforeexposure processing of a lot, said controller obtains a correction valuefor a measurement error due to factors associated with acceleration ofsaid stage using at least one substrate belonging to the lot, andexposes substrates belonging to the lot using the obtained correctionvalue.
 3. An exposure method of projecting a pattern of a reticle onto asubstrate via a projection optical system using slit-shaped light whilescanning the reticle and the substrate in a first direction, therebyexposing the substrate, the method comprising the steps of: measuring alevel of the substrate that is a position of the substrate in a seconddirection parallel to an optical axis of the projection optical systemat a predetermined position on the substrate while a stage which holdsthe substrate accelerates, at a first measurement point at which thelevel of the substrate can be measured earliest among a plurality ofmeasurement points located with spacings therebetween in the firstdirection for a measurement device, and measuring the level of thesubstrate at the predetermined position while the stage moves at aconstant velocity, at a second measurement point within a region inwhich the slit-shaped light is incident on the substrate; calculating adifference between the measurement results of the level of the substrateat the predetermined position, which are obtained at the firstmeasurement point and the second measurement point, respectively, toobtain the calculated difference as a correction value for a measurementerror due to factors associated with acceleration of the stage; andmeasuring the level of the substrate at the first measurement pointusing the measurement device, and exposing the substrate whilepositioning the stage in the second direction based on the levelmeasured at the first measurement point, wherein when the substrate isexposed at a given position on the substrate after the level of thesubstrate at the given position is measured at the first measurementpoint while the stage accelerates, the level of the substrate measuredat the first measurement point is corrected using the obtainedcorrection value and the substrate is exposed while positioning thestage so that the level of the substrate at the given position becomesequal to the level corrected using the correction value, and, when thesubstrate is exposed at a given position on the substrate after thelevel of the substrate at the given position is measured at the firstmeasurement point while the stage moves at a constant velocity, thesubstrate is exposed while positioning the stage so that the level ofthe substrate at the given position becomes equal to the level measuredat the first measurement point.
 4. A method of manufacturing a device,the method comprising: exposing a substrate using an exposure apparatuswhich projects a pattern of a reticle onto a substrate via a projectionoptical system using slit-shaped light while scanning the reticle andthe substrate, thereby exposing the substrate; developing the exposedsubstrate; and processing the developed substrate to manufacture thedevice, wherein the exposure apparatus comprises a stage which holds thesubstrate, a positioning mechanism which positions the stage in a firstdirection to scan the substrate and a second direction parallel to anoptical axis of the projection optical system, a measurement devicewhich measures a level of the substrate that is a position of thesubstrate in the second direction at a plurality of measurement pointslocated with spacings therebetween in the first direction, and acontroller, the plurality of measurement points include a firstmeasurement point at which the level of the substrate can be measuredearliest, and a second measurement point within a region in which theslit-shaped light is incident on the substrate, the exposure apparatusis configured to measure the level of the substrate at the firstmeasurement point using the measurement device, and expose the substratewhile positioning the stage in the second direction using thepositioning mechanism based on the level measured at the firstmeasurement point, and the controller causes, before the substrate isexposed, the measurement device to measure the level of the substrate ata predetermined position on the substrate at the first measurement pointwhile the stage accelerates, and measure the level of the substrate atthe predetermined position at the second measurement point while thestage moves at a constant velocity, calculates a difference between themeasurement results of the level of the substrate at the predeterminedposition, which are obtained at the first measurement point and thesecond measurement point, respectively, to obtain the calculateddifference as a correction value for a measurement error due to factorsassociated with acceleration of the stage, and corrects the level of thesubstrate measured at the first measurement point using the obtainedcorrection value and exposes the substrate while controlling thepositioning mechanism so that the level of the substrate at a givenposition on the substrate becomes equal to the level corrected using thecorrection value, when the substrate is exposed at the given positionafter the level of the substrate at the given position is measured atthe first measurement point while the stage accelerates, and exposes thesubstrate while controlling the positioning mechanism so that the levelof the substrate at a given position on the substrate becomes equal tothe level measured at the first measurement point, when the substrate isexposed after the level of the substrate at the given position ismeasured at the first measurement point while the stage moves at aconstant velocity.